1. Field of the Invention
The present invention relates to a composite electronic component including circuit elements such as a capacitor, an inductor, and other elements, and a method of producing such a composite electronic component.
2. Description of the Related Art
FIG. 11 shows a conventional high frequency composite electronic component of the related art, in which an electronic component 9 is mounted onto a laminate type substrate 1 including circuit elements such as a capacitor and an inductor, and a metallic case 7 is integrated with them. A grounding external electrode 4 and input-output external electrodes 5 are disposed on side surfaces 2 and 3 of the laminate type substrate 1 (also on the opposite side surfaces). A terminal 8 of the metallic case 7 is soldered to the grounding external electrode 4.
As described in Japanese Unexamined Patent Application Publication No. 6-96992 by the applicant of the present invention, as shown in FIG. 12, via-holes 11 and 12 filled with conductive members (conductive paste) 4xe2x80x2 and 5xe2x80x2 are formed along cut lines A and B in a mother ceramic green sheet 10 (hereinafter, referred to as a via-hole filling process). A mother laminate is cut along the cut lines A and B, whereby the conductive members 4xe2x80x2 and 5xe2x80x2 are exposed at the side surfaces 2 and 3.
However, the via-holes 11 have a large, elongated rectangular cross-section, respectively. Accordingly, the conductive paste tends to be insufficiently filled into the via-holes 11. Thus, there is a danger in that the conductive paste is released, deficient grounding external electrodes 4 are formed by firing, and the reliability of electrical connection of the external electrode 4 to the internal circuit elements and the terminal 8 of the metallic case becomes insufficient.
As countermeasures against the above-described problems, an attempt was made to increase the number of times which the conductive paste is filled. This caused problems in that the conductive paste was excessively filled, and cracks were formed in the external electrode 4, due to the difference between the firing shrinkage ratios of the conductive paste and a ceramic sheet.
Furthermore, the via-holes 11 having an elongated rectangular cross-section have problems in that inevitably, the contact area between the external electrode 4 and the ceramic raw laminate is small, and the bonding strength is low.
In order to overcome the problems described above, preferred embodiments of the present invention provide a composite electronic component which is provided with external electrodes having a high reliability of electrical connection and a excellent bonding strength for bonding to a ceramic laminate, and a method of producing such a novel composite electronic composite.
According to a preferred embodiment of the present invention, a composite electronic component including a laminate including a plurality of insulation sheets laminated with internal circuit elements being interposed between the insulation sheets, external electrodes electrically connected to the internal circuit elements and disposed on side surfaces of the laminate, and a metallic case arranged to cover at least a portion of the upper surface of the laminate and having terminals electrically connected to the external electrodes, the external electrodes being arranged such that a plurality of external electrodes are provided on at least one side surface of the laminate and electrically connected to the same terminal of the metallic case.
In the composite electronic component of preferred embodiments of the present invention, preferably, the external electrodes are made of the conductive material used to form the conductive members disposed in the plurality of the via-holes formed in the insulation sheets. The cross-section of the via-holes may preferably be substantially quadrangular, substantially circular, or substantially elliptic, instead of being elongated-rectangular as in the related art. By providing appropriate amounts of the conductive members, release of the conductive members from the via-holes and formation of cracks can be prevented, and thus, the electrical connection has greatly improved reliability. Moreover, the contact area between the external electrodes and the raw laminate is increased, and the bonding strength of the external electrodes is greatly improved.
The plurality of the external electrodes may be arranged substantially parallel to each other in the lamination direction of the laminate, and may be electrically connected to each other via conductive members which are arranged to extend substantially perpendicularly to the lamination direction of the laminate. Thus, the surface area of the external electrodes is increased, and the contact area thereof to the terminal of the metallic case is also increased. The connection reliability is thereby greatly improved. The conductive members may be positioned so as to contact with the mounting surface of the laminate. Accordingly, the reliability of connection between the external electrodes and the terminal of the metallic case is greatly improved, and moreover, the external electrodes and a land of a packaging substrate can be securely soldered.
According to another preferred embodiment of the present invention, a method of producing a composite electronic component includes the steps of forming via-holes in mother sheets along cut lines provided on the mother sheets, the via-holes having conductive paste for electrical connection thereof to internal circuit elements applied therein, laminating a plurality of the mother sheets with internal circuit elements being interposed between mother sheets, cutting the laminate of the mother sheets along the cut lines to expose a plurality of solidified paste members applied into the via-holes onto at least one side surface of the laminate whereby external electrodes are formed, and connecting the plurality of the external electrodes on the same side surface to the same terminal of a metallic case which covers at least a portion of the upper surface of the laminate.
According to the method of producing the composite electronic component of a preferred embodiment of the present invention, the external electrodes are preferably formed using the conductive paste applied in the plurality of the via-holes. The cross-section of the via-holes may be substantially quadrangular, substantially circular, or substantially elliptic, instead of being elongated-rectangular as in the related art. By providing appropriate amounts of the conductive members, release of the conductive members from the via-holes and formation of cracks, which may occur at firing, are reliably prevented, and thus, the electrical connection has a greatly improved reliability. Moreover, the contact area between the external electrodes and the laminate is significantly increased, and the bonding strength of the external electrodes is greatly improved.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.